Telephone system



Dec. 29, 1925- 1,567,305 E. H. SMYTHE TELEPHONE SYSTEM Filed Dec. 24, 1923 wimmlm c Patented Dec. 29, 1925.

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EDW'IN H. SMYTHE, OF EVANSTON, ILLINOIS. ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK. N. Y1, A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed December 24, 1923.

To all whom it may concern:

Be it known that I, EDWIN H. SMY'rHn, a citizen of the United States, residing at Evanston, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and e; act description.

This invention relates to telephone systems and particularly to subscriber controlled machine switching systems. Its object is to provide in a step-bystep system means for enlarging the capacity of an exchange which is restricted in line numbers; in other words, to provide an exchange li1n ited as'to line numbers but unlimited as to lines.

In accordance with this object a step-by step switch is provided with a registermarker in the form of a set of counting relays which respond to impulses sent from a calling substation and indicate to the switch the extent of its primary movement. In its broad aspects, such a scheme has heretofore been disclosed in Patent No. 1,274,654 issued to J. L. lVright, August 6. 1918. The present invention however, provides an im proved arrangement whereby the distance traversed by the switch per impulse is variableso that while the point marked by the register corresponds to the number of impulses received as in the prior art disclosure, such point does not correspond in its spacial relation with such number of impulses. This new arrangement produces this result, that a so-called P. B. X. connector may be provided wherein one line number designates a whole group of lines and such group is limited only by the mechanical capacity of the switch. Hence, this invention renders it possible and practicable to provide an unlimited number of lines in an exchange having a limited capacity in line numbers.

Another feature of the invention resides in means for varying at will the size of the trunk groups and rearranging line terminals on a connector switch without disturbing the line numbering arrangement.

The invention is disclosed in a single sheet of drawing which illustrates diagrammatically only so much of the system as is Serial No. 682,368.

necessary for a full understanding of the principles involved.

The subscriber at substation A in removing his receiver from its switehhook causes the line switch 1 to be set in the ordinary manner so as to extend his line to the selector switch 2. This he sets under directive control of his sender and thereby extends his line to the connector switch torm ing the body of the drawing. Such connector switch is in the form of a single motion rotary step-by-step switch and may be provided with any suitable number of terminals. Since this switch is designed to be set under control of the units series of impulses alone, it has to provide for ten digital places and so if the trunk groups which itis to serve are small the capacity of the switch itself will be small. If, however, it is to serve a plurality of large trunk groups the switch may be of large capacity. Switches oi this type are made with terminal banks of different capacity and the circuit arangemcnt provided by this invention is such that these switches may be interchangeably used so that where the trunk groups served b y one switch have outgrown its capacity a larger capacity switch may be installed without in any manner chang ing the line numbering arrangement or the circuit arrangement.

\Vhcn the line of substation A has been extended to the connector switch, the line relay 3 will become energized. The energization of this relay closes a circuit for the slow releasing relay elwhich extends ground to the test conductor of the selector switch 2 for holding purposes in the well known manner. The energization of relay l also prepares a circuit for relay 5.

For purposes of illustration we will first assume that the subscriber at substation A sends a single impulse, such impulse being in reality a short interruption of the line circuit. It should be noted that this terminology is employed since it is common practice among telephone engineers and plant men to speak of the interruptions caused by the modern substation sender as impulses. This results in the momentary deenergization of relay 3 whereupon a circuit is closed from battery, the armature and back contact of relay 3, right hand armature and front contact of relay a, winding of relay 5 to ground. Relay 5 becoming energized extends a connection from ground, outer right hand armature and back contact 'of'rela'y'tl, armature and front contact of relay 5, normal contacts of the right hand armature of relay 7, Winding of relay 7, back contact and inner right hand armature of relay 6 to battery and ground. Relay '7 becomes energized and locks up in a circuit from ground, its own right hand armature and front contact. This action extends a ground to the normal terminal on which brush 8 rests with a result which will be hereinafter described.

Upon the ending of'the first impulse re lay 3 att'acts its armature and causes the deenergization of relay 5 whereupon a circuit is extended from ground, the outer right hand armature and back contact of relay 6, the armature and back contact of relay 5, the normal contactof the right hand armature of relay 9 Winding of relay 9, front contact and left hand armature of relay 7, back contact and inner right hand armature bf relay 6 to battery and ground, whereupon relay 9 locks up in a circuit including its own right hand armature and front' contact and at the same time extends a ground to the second terminal traversed by brush 8. i

The ground extended to brush 8 by the right hand armature of relay 7 is connected through the back contact and outer left hand armature of relay 6, Winding of relay 10 to battery and ground. Relay 10 becomes energized and establishes a connection from ground through the front contact and armature of relay 10 to a point Where the circuit divides extending in one direction through the Winding of slow releasing relay 11 to battery and ground and in the other direction through the bacltcontact, armature and inding of motor magnet 12 to battery and ground. Motor magnet 12 becoming energized opens its own circuit and moves the brushes 13, 14C, 15 and 8 forward onestep. As brush 8 leaves the terminalconnected to relay 7 it opens the circuit of relay 10 and relay 10 beeomes deenergized momentarily. Relay 11 being slow releasing however maintains its armature energized to prevent the establishment of aneifective circuit through the offnormal contact '16 which has become closed upon the first step of the switch. brush 8 "comes" in c 'ontactwith the terminal associated with relayQ, relay 10 becomes again ized whereupon the motor magnet 12 hay ngin the meantime retracted its armature becomes energized to -step'the brushes forward gf's eenu" step. When the brush 8' comes in contact with its third terminal which is'associated with the next registereilie re y he e W l b 12' qmictioe to ground so that relay 10 Will remain deenergized and the motor magnet will not become energized to step the brushes further on. After an interval relay 11 will become deenergized and the line on which the brushes have been set will be tested for its idle or busy condition.

Let us assume that the calling subscriber sends out a series of three impulses instead of one. The second impulse Will then cause the energization of relay 17 and thereafter relay 18 and the third impulse will first cause the energization of relay 19 and thereafter the energization of relay 20 so that all ,of the terminals over which brush 8 traverses until terminal. 21 is reached Will be con nected to ground. The switch Will move forward as before described, relay 10 energizing and deenergizing as the brush 8 comes in contact with the separate terminals, relay 11 in the meantime remaining ener gized in the manner described. When finally brush 8 reaches terminal 21, relay 10 Will fail to energize and the switch will stop its forward movement. In a short interval relay 11 will become energized whereupon a circuit will be extended from ground, the off-normal contact 16, the armature and back contact of relay 11, the left hand winding of relay 22, the normal contact of the inner left hand ari'nature of relay 6, Winding of relay 6 to battery and ground. Relay 6 becomes energized in this circuit and locks tl rough its alternate contact and inner left hand armature to the ground on the offnornial contact 16. The energization of relay 6 releases the register-marker relays.

We Will assume that the line connected to the terminals corresponding to the terminal 21 is busy and that the rest of the lines in the same group up to the one associated With terminal are o busy. Under this assumption ground supplied over the outer right-hand armature and front contact of relay 6, Winding of relay 32, back contact and armature of relay 22, right-hand armature in d back contact of relay 29 and brush 15 of similar switches Which have engaged these terminals, ill be found on each of terminals .13, 2e, 25, 26, 27 and 28. There fore, upon the energization of relay .6 and the energization of relay 22 in series therewith, a circuit will be extended from ground on terminal 23, brush 15, the back contact and armature of release relay 29, right hand armature and front contact of relay 22, right hand Winding of relay 22, front contact and outer left hand armature of relay 6, Winding of relay 10 to battery and ground. Relay 10 becomes energized in this circuit and relay 22 remains energized in series therewith. The energization of relay 10 results in the energization of slow releasing relay 11 and motor magnet 12 in the manner hereinbeo esc bed, s t th sh 'ef he.

switch will now be moved forward step by step, until brush 15 engages terminal 30, which wewill assume is associated with an idle line. This will result in the establishment of a circuit including relay 10 and relay 31, both of which being connected to battery, result in the non-energization of relay 31 and the deenergization of relay 10. In a short interval relay 22 retracts its armature whereupon a circuit will be established from ground, the outer right hand armature and front contact of relay 6, the winding of relay 32, the back contact and armature of relay 22, armature and back contact of relay 29, brush l5, terminal 30, winding of cut-off relay 31 to battery and ground. Relays 31 and 32 become energized in this circuit with the following result: A circuit is established from ground, front contact and armature of relay 32, back contact and armature of relay 33, back contact and outer lower armature of relay 34, winding of relay to battery and ground. Relay 35 becomes energized and connects ringing current to the called substation, such current traversing a circuit from the source of ringing current 36, front contact and inner armature of relay 35, the winding of relay 33, back contact and inner lower armature of relay 34, brush 14, over the line of substation B, brush 13, upper armature and back contact of relay 34, outer armature and front contact of relay 35 to ground. The current traveling in this circuit is insufficient to cause the energization of relay 33 but when the subscriber at substation B removes his receiver, or the operator at such place answers the call, the current will be increased to an amount sufiicient to cause the energization of relay Thereupon a circuit will be established from ground, front contact and armature of relay 32, winding of relay34, winding of relay 35 to battery and ground. Thus relay 34 becomes energized and locked up to battery and ground at its lowermost armature and front contact, and relay 35 is short circuited with the result that the ringing current is cut olf from the calling subscribers line and the'talking path between substations A and B is completed. Talking battery for the called substation is supplied over the windings of relay 37.

At the end of the conversation when the subscriber at substation A hangs up his receiver relay 3 will become deenergized and in a short interval thereafter relay 4 will retract its armatures whereupon a circuit will be established from battery, armature and back contact ofrelay 3, right hand armature and back contact of relay 4, winding of re lease relay 29 through the off-normal contact 16 to ground. Relay 29 becoming energized closes a circuit from ground at the off-normal contact 16 through the left hand armature and front contact of relay 29 to the back contact and armature of relay 10 which causes the movement of the brushes of the connector switch to their normal position whereupon the off-normal contact 16 is opened and all of the relays tied to this ground will be released.

Let us assume that the line of substation B had been busy, then when brush 15 had encountered terminal 30 relay 10 would again have become energized and the brushes would be stepped to the next set of terminals. Thereupon a circuit will become established from ground, outer right hand armature and front contact of relay 6, winding of relay 32, back contact and armature of relay 22, the armature and back contact of relay 29, brush 15, terminal 38, winding of relay 39 to battery and ground. Relay 39 will become energized in this circuit but relay 32 being marginal will not attract its armature. The failure of relay 32 to be come energized prevents the application of ringing current to the brushes 13 and 14. The energization of relay 39 connects the source of busy tone 40 over the front contact and armature of relay 39, the back contact and armature of relay 3?, the right hand winding of relay 37 to battery and ground whence by induction, the busy tone is transmitted to the calling substation A.

Upon the replacing of the receiver on its hook at the calling substation A the switch becomes released in the manner hereinbefore described.

It will be noted that through the circuit arrangement herein employed the impulses from the calling substation may be registered at high speed since the relays 7, 9, 17 to 20, etc., are quick acting relays. The switch itself may advance quickly or slowly, the rate of its movement being immaterial since this switch is responsive to the final digit of a call number and since the ground will be maintained on the terminals associated with brush 8 until the relay 6 becomes energized upon the change-over from the primary or directed movement of the switch to its automatic line selection movement.

It will further be noted that in the illustration herein contained three groups of lines are shown, the first group consisting of a single line, the second group consisting of four lines and the third group consisting of seven lines. Thus the line groups are unequal and the primary movement of the switch is not a measure in actual steps of the number of impulses re ceived. If it is found necessary, for instance, to enlarge the second trunk group by one line, the conductor leading from relay 41 to terminal 21 may be connected to terminal 42 and appropriate connections thereafter be made to the corresponding terminals of this row so that a trunk group may be enlarged without disturbing the line numbering arrangement at all. Through this arrangement a' single number is employed to .designate an indefinite and variable number of lines.

What is claimed is:

1. In a telephone system, a selector switch, a register-marker individual to said switch for determining one factor in the extent of the primary movement of said switch, and means variable at will for determining another factor in the extent of the primary movement of said switch.

2. In a telephone system, a selector switch, a register1narker individual to said switch and responsive to impulses for determining one factor in the extent of the primary movement of said switch, means variable at will for determining another factor in the extent of the primary movement of said switch, means for starting said switch during the registration of impulses, and means for maintaining the said registration until the primary movement of said switch is complete.

3. In a telephone system, a selector switch, a register-marker individual to said switch comprising counting relays responsive to impulses for determining one factor in the extent of the primary movement of said switch, means variable at will for determining another factor in the extent of the primary movement of said switch, means for starting said switch upon the registration of the first impulse, means for moving the switch forward continuously if the registration of the impulse is quicker than the movement of the switch, and means for moving the switch forward haltingly if the registration of the impulses is slower than the movement of the switch.

4. In a telephone system, a selective switch, a register-marker individual to said switch .comprising counting relays responsive to impulses for determining one factor in the extent of the primary movement of said switch, means variable at will for determining another factor in the extent of the primary movement of said switch, and

means for moving said switch forward at a I rate approaching but not exceeding synchronism with the registration of said impulses.

5. In a telephone system, a travelling switch, a register-marker individual to said switch controlled by impulses for controlling said switch, and means changeable at will for varying the extent of the switch movement per impulse.

6. In a telephone system, a connector switch, consecutively numbered groups of subscribers lines connected to said switch, said groups being serially arranged and variable in size, an individual registermarker responsive to impulses and operable to select any desired group, and means oper able to cause said switch to seize the first idle line therein.

7. In a telephone system, a single motion connector switch, consecutively numbered groups of subscribers lines connected to said switch, said groups being serially arranged and variable in size, a registermarker individual to saidswitch responsive to impulses and operable to select any desired group, and means operable to cause said switch to seize the first idle line therein.

8. In a telephone system, a selector switch, consecutively numbered and serially arranged groups of lines connected to said switch, each group comprising a plurality of unnumbered lines and a single numbered line, a register-marker individual to said switch and responsive to impulses operable to select a numbered line, and means effective thereafter to cause said switch to seize the first idle line in the group selected.

In witness whereof, I hereunto subscribe my name this 17th day of December A. D., 1923.

EDWIN SMYTHE. 

